Do I need a subdivision modifier to create a hard-surfaced object
This is really a subjective topic and I don't think it can be answered with 100% certainty for you. Some high-level modelers will use sub-d's on a model like this, while others will not; it just depends on the the person and not necessarily the model, although the model itself is a factor.

You also have to consider how the model is going to be used: Is it going to be for a game or animated in some way? Will it have a UV map? Just a still image? If so, how big will the image be and how long are you willing to wait for it to render? A sub-d model will render better generally, but will take longer. All these things must be taken into account.

One thing to note: When you say "hard surface" that doesn't exclude a model with subdivision surfaces on it, and you can have organic models with no subdivision at all -- it just depends on what you are trying to achieve. Just understand that it will be more difficult to get smooth, rounded areas without some level of subdivision.

You'll just have to try it both ways (or a combination of both) and find out what works best for you. There's no rule that says you have to only do things one way. That's the best answer I can give you.